In a communications system based on IEEE 802.11 (or also widely known as Wi-Fi), both physical and virtual carrier sensing (CS) functions are used to determine the state of the medium (i.e., the channel). When either function indicates a busy channel, the channel is considered busy; otherwise, it is considered idle. A physical CS function is based on comparing the energy detected on the channel and a detection threshold that is pre-specified per frequency band and channel bandwidth. A virtual CS function is provided by the medium access control (MAC) layer of IEEE 802.11 compliant communications systems using a network allocation vector (NAV). The virtual CS function indicates the state, e.g., idle or busy, of a channel. The NAV is an indicator that is maintained by each Wi-Fi station and access point (AP) of time periods when transmissions onto the channel is not to be initiated by the station or AP. Any station or AP receiving a valid frame where a value in an Address 1 field (also known as the Receiver Address (RA) field) in the MAC header of the frame is not the MAC address of the station or AP should update its NAV with the value received in the Duration field of the MAC header of the frame. The NAV may be thought of as a counter that counts down to 0 at a uniform rate. When the NAV reaches 0, the virtual CS function indicates that the channel is idle and when the NAV is nonzero, the virtual CS function indicates that the channel is busy. When the channel is busy, the channel cannot or should not be accessed.